Ultra-conformal carbon film deposition

ABSTRACT

Embodiments of the disclosure relate to deposition of a conformal carbon-based material. In one embodiment, the method comprises depositing a sacrificial dielectric layer over a substrate, forming patterned features on the substrate by removing portions of the sacrificial dielectric layer to expose an upper surface of the substrate, introducing a hydrocarbon source, a plasma-initiating gas, and a dilution gas into the processing chamber, generating a plasma in the processing chamber at a deposition temperature of about 80° C. to about 550° C. to deposit a conformal amorphous carbon layer on the patterned features and the exposed upper surface of the substrate, selectively removing the amorphous carbon layer from an upper surface of the patterned features and the upper surface of the substrate using an anisotropic etching process to provide the patterned features filled within sidewall spacers, and removing the patterned features formed from the sacrificial dielectric layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/770,412, filed Aug. 25, 2015, which is a National Stageentry of International Patent Application Serial No. PCT/US2014/016604,filed Feb. 14, 2014, which claims benefit of U.S. provisional patentapplication Ser. No. 61/793,979, filed Mar. 15, 2013, each of which areherein incorporated by reference.

BACKGROUND Field

Embodiments of the present disclosure generally relate to thefabrication of integrated circuits and particularly to a method forprotecting sidewalls of hard mask spacers during an etching process.

Description of the Related Art

Reducing the size of integrated circuits (ICs) results in improvedperformance, increased capacity and/or reduced cost. Each size reductionrequires more sophisticated techniques to form the ICs. Photolithographyis commonly used to pattern ICs on a substrate. An exemplary feature ofan IC is a line of a material which may be a metal, semiconductor orinsulator. Linewidth is the width of the line and the spacing is thedistance between adjacent lines. Pitch is defined as the distancebetween a same point on two adjacent lines. The pitch is equal to thesum of the linewidth and the spacing. Due to factors such as optics andlight or radiation wavelength, however, photolithography techniques havea minimum pitch below which a particular photolithographic technique maynot reliably form features. Thus, the minimum pitch of aphotolithographic technique can limit feature size reduction.

Double patterning processes are widely employed in the patterning of 3×and beyond features. Self-aligned double patterning (SADP) is one doublepatterning process used for extending the capabilities ofphotolithographic techniques beyond the minimum pitch. Such a method isillustrated in FIGS. 1A-1F. With reference to FIG. 1A, patterned corefeatures 102 are formed from sacrificial structural material above adielectric layer 114 on a substrate 100 using standard photo-lithographyand etching techniques. The patterned features are often referred to asplaceholders or cores and have linewidths and/or spacings near theoptical resolution of a photolithography system using a high-resolutionphotomask. As shown in FIG. 1B, a conformal layer 106 of hard maskmaterial is subsequently deposited over core features 102. Hard maskspacers 108 are then formed on the sides of core features 102 bypreferentially etching the hard mask material from the horizontalsurfaces with an anisotropic plasma etch to open the hard mask materialdeposited on top of the patterned core features 102 as well as removethe hard mask material deposited at the bottom between the twosidewalls, as shown in FIG. 10. The patterned core features 102 may thenbe removed, leaving behind hard mask spacers 108 (FIG. 1D). At thispoint hard mask spacers 108 may be used as an etch mask for transferringthe pattern to the dielectric layer 114 to form dielectric ribs 116, asshown in FIG. 1E. The hard mask spacers 108 are subsequently removed(FIG. 1F). Therefore, the density of the dielectric ribs 116 is twicethat of the photo-lithographically patterned core features 102, and thepitch of the dielectric ribs 116 is half the pitch of the patterned corefeatures 102.

Currently, hard mask spacers 108 are formed by an atomic layerdeposition (ALD) using an etchable material such as silicon oxides.These oxides are typically deposited at very low temperature (e.g., lessthan 200° C.). As a result, these hard mask spacers are not compatiblefor high temperature application. In addition, the deposited materialquality is poor, with low density and poor mechanical strength anddegraded chemical resistance to subsequent etching chemistries.Moreover, oxides spacer materials require wet clean process for removalafter etching. Wet clean is an isotropic process which typically leadsto CD loss and under-cut issues. Therefore, a dry-strippable spacermaterial is highly desirable.

Amorphous carbon has been a decent alternative for etch hard maskmaterial due to its easy strippability using conventional dry ashingprocess. This enables selective removal of carbon films withoutaffecting other surrounding materials such as SiO₂, SiN, etc. One of themajor challenges in amorphous carbon deposition is to achieveconformality with minimum pattern loading effect, gap filling andplanarization capabilities on high aspect ratio structures.

Therefore, there is a need for an improved method of depositing highlyconformal amorphous carbon film with minimal or no pattern micro-loadingwhile preserving the mechanical properties such as density, hardness andmodulus.

SUMMARY

Embodiments of the present disclosure relate to deposition of anultra-conformal carbon-based material. In one embodiment, the methodcomprises depositing a sacrificial dielectric layer with a predeterminedthickness over a substrate, forming patterned features on the substrateby removing portions of the sacrificial dielectric layer to expose anupper surface of the substrate, introducing a hydrocarbon source, aplasma-initiating gas, and a dilution gas into the processing chamber,wherein a volumetric flow rate of hydrocarbon source:plasma-initiatinggas:dilution gas is in a ratio of 1:5:20, generating a plasma in theprocessing chamber at a deposition temperature of about 80° C. to about550° C. to deposit a conformal amorphous carbon layer on the patternedfeatures and the exposed upper surface of the substrate, selectivelyremoving the amorphous carbon layer from an upper surface of thepatterned features and the upper surface of the substrate using ananisotropic etching process to provide the patterned features filledwithin sidewall spacers formed from the conformal amorphous carbonlayer, and removing the patterned features formed from the sacrificialdielectric layer.

In another embodiment, a method of forming a conformal amorphous carbonlayer on a substrate in a processing chamber is provided. The methodcomprising forming patterned features on an upper surface of asubstrate, depositing a conformal sacrificial dielectric layer on thepatterned features and an exposed upper surface of the substrate,selectively removing the sacrificial dielectric layer from an uppersurface of the patterned features and the exposed upper surface of thesubstrate to provide the patterned features filled within first sidewallspacers formed from the sacrificial dielectric layer, forming secondsidewall spacers adjacent or in contact with the first sidewall spacers,comprising introducing a hydrocarbon source, a plasma-initiating gas,and a dilution gas into the processing chamber, wherein a volumetricflow rate of hydrocarbon source:plasma-initiating gas:dilution gas is ina ratio of 1:0.5:20, generating a plasma in the processing chamber at adeposition temperature of about 80° C. to about 550° C. to deposit aconformal amorphous carbon layer on the patterned features and theexposed upper surface of the substrate, and selectively removing theamorphous carbon layer from the upper surface of the patterned featuresand the upper surface of the substrate using an anisotropic etchingprocess, and removing the patterned features filled within the firstsidewall spacers.

In yet another embodiment, the method includes depositing a dielectriclayer on a substrate, depositing a sacrificial dielectric layer on anupper surface of the dielectric layer, forming a pattern into thesacrificial dielectric layer by removing portions of the sacrificialdielectric layer to expose portions of the upper surface of thedielectric layer, introducing a hydrocarbon source, anitrogen-containing gas, a plasma-initiating gas, and a dilution gasinto the processing chamber, wherein a volumetric flow rate ofhydrocarbon source:nitrogen-containing gas:plasma-initiatinggas:dilution gas is in a ratio of about 1:0.5:0.5:20, generating aplasma in the processing chamber at a deposition temperature of about75° C. to about 650° C., a chamber pressure of about 2 Torr to about 15Torr, and an electrode spacing of about 200 mils to about 1000 mils todeposit a conformal amorphous carbon layer on the portions of the uppersurface of the dielectric layer and on remaining portions of thesacrificial dielectric layer, wherein the plasma is generated byapplying RF power at a power density to substrate surface area fromabout 0.04 W/cm² to about 0.07 W/cm², selectively removing the amorphouscarbon layer using an anisotropic etching process to expose uppersurfaces of the remaining portions of the sacrificial dielectric layerand to expose the upper surface of the dielectric layer, and removingthe remaining portions of the sacrificial dielectric layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIGS. 1A-1F illustrate cross-sectional views representing a conventionaldouble patterning process.

FIG. 2 is a flowchart depicting steps associated with an exemplarypatterning process according to one embodiment of the disclosure.

FIGS. 3A-3E illustrate cross-sectional views of a structure formed bythe flowchart set forth in FIG. 2.

FIG. 4 is a flowchart depicting steps associated with an exemplarypatterning process according to another embodiment of the disclosure.

FIGS. 5A-5H illustrate cross-sectional views of a structure formed bythe flowchart set forth in FIG. 4.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to deposition of anultra-conformal carbon-based material. In various embodiments, anultra-conformal carbon-based material, such as amorphous carbon, isdeposited over features of sacrificial structure material patternedusing a high-resolution photomask. In one example, the ultra-conformalcarbon-based material serves as a protective layer during an ashing oretching process, leaving the sacrificial structure material with anupper surface exposed and sidewalls protected by the carbon-basedspacers. Upon removal of the sacrificial structure material, theremaining carbon-based spacers may perform as a hardmask layer foretching the underlying layer or structure. While the process describedherein is mainly related to a spacer application using carbon-basedmaterial, the improved process of the disclosure is also applicable toother applications which may require a conformal amorphous carbon filmsuch as gap fill, hard mask for hot ion implantation, feature holeshrinking or protection for semiconductor devices, or healing of lineedge roughness for device nodes.

Embodiments of the present disclosure may be performed using anysuitable processing chamber such as a plasma enhanced chemical vapordeposition (PECVD) chamber. The processing chamber may be incorporatedinto a substrate processing system. An exemplary substrate processingsystem that may be used to practice the disclosure is described incommonly assigned U.S. Pat. No. 6,364,954 issued on Apr. 2, 2002, toSalvador et. al. and is herein incorporated by reference. Examples ofsuitable systems include the CENTURA® systems which may use a DxZ™processing chamber, PRECISION 5000® systems, PRODUCER™ systems, PRODUCERGT™ and the PRODUCER SE™ processing chambers which are commerciallyavailable from Applied Materials, Inc., Santa Clara, Calif. It iscontemplated that other deposition processing system, including thoseavailable from other manufacturers, may be adapted to practice theembodiments described herein.

FIG. 2 is a process flowchart depicting steps associated with anexemplary self-aligned double patterning (SADP) process according to oneembodiment of the disclosure. FIGS. 3A-3E illustrate cross-sectionalviews of a structure formed by the steps set forth in FIG. 2. It iscontemplated that the self-aligned double patterning process is chosenfor illustration purpose. The concept of the disclosure is equallyapplicable to other deposition processes or patterning schemes, such asa self-aligned triple patterning (SATP) process, a self-alignedquadruple patterning (SAQP) process, a via/hole shrink process, a backend of line (BEOL), etc., that may require the use of protective spaceror protective sacrificial layer, as needed in various semiconductorprocesses such as NAND flash application, DRAM application, or CMOSapplication, etc.

The process 200 starts at box 202 by forming a sacrificial structurallayer 320 on a substrate 300. The sacrificial structural layer 320 maybe a silicon-based material such as silicon oxide, silicon nitride,silicon oxynitride, silicon carbides, or polysilicon. It is contemplatedthat the choice of materials used for the sacrificial structural layer320 may vary depending upon the etching/ashing rate relative to theconformal protective layer to be formed thereon.

While not shown, one or more anti-reflective coating layers may bedeposited on the sacrificial structural layer 320 to control thereflection of light during a lithographic patterning process. Suitableanti-reflective coating layer may include silicon dioxide, siliconoxynitride, silicon nitride, or combinations thereof. One exemplaryanti-reflective coating layer may be a DARC™ material commerciallyavailable from Applied Materials, Inc. of Santa Clara, Calif.

The substrate 300 may have a substantially planar surface 323 as shown.Alternatively, the substrate 300 may have patterned structures, asurface having trenches, holes, or vias formed therein. While thesubstrate 300 is illustrated as a single body, the substrate 300 maycontain one or more materials used in forming semiconductor devices suchas metal contacts, trench isolations, gates, bitlines, or any otherinterconnect features. In one embodiment, the substrate 300 may includeone or more metal layers, one or more dielectric materials,semiconductor material, and combinations thereof utilized to fabricatesemiconductor devices. For example, the substrate 300 may include anoxide material, a nitride material, a polysilicon material, or the like,depending upon application. In cases where a memory application isdesired, the substrate 300 may include the silicon substrate material,an oxide material, and a nitride material, with or without polysiliconsandwiched in between.

In some embodiments, the substrate 300 may include a plurality ofalternating oxide and nitride materials (i.e., oxide-nitride-oxide(ONO)), one or more oxide or nitride materials, polysilicon or amorphoussilicon materials, oxides alternating with amorphous silicon, oxidesalternating with polysilicon, undoped silicon alternating with dopedsilicon, undoped polysilicon alternating with doped polysilicon, orupdoped amorphous silicon alternating with doped amorphous silicondeposited on a surface of the substrate (not shown). The substrate 300may be a material or a layer stack comprising one or more of thefollowing: crystalline silicon, silicon oxide, silicon oxynitride,silicon nitride, strained silicon, silicon germanium, tungsten, titaniumnitride, doped or undoped polysilicon, doped or undoped silicon wafersand patterned or non-patterned wafers, silicon on insulator (SOI),carbon doped silicon oxides, silicon nitrides, doped silicon, germanium,gallium arsenide, glass, sapphire, low k dielectrics, and combinationsthereof.

At box 204, a resist layer 330, such as a photoresist material, isdeposited on the sacrificial structural layer 320 and patterned with adesired pitch as shown in FIG. 3A.

At box 206, patterned features 321 formed from the sacrificialstructural layer 320 are produced on the substrate 300, using the resistlayer 330 as a mask, by standard photo-lithography and etchingtechniques, as shown in FIG. 3B. The patterned features are sometimesreferred to as placeholders, mandrels or cores and have specificlinewidth and/or spacing based upon the photoresist material used. Thewidth of the patterned features 321 may be adjusted by subjecting theresist layer 330 to a trimming process. After the pattern has beentransferred into the sacrificial structural layer 320, any residualphotoresist and hard mask material (if used) are removed using asuitable photoresist stripping process.

At box 208, a carbon-based protective layer 340 is deposited conformallyor substantially conformally on the patterned features 321 and theexposed surfaces of the substrate 300, as shown in FIG. 3C. Thecarbon-based protective layer 340, when deposited using novel processconditions discussed below, will achieve step coverage of at least about80% or more, for example about 100% or more, such as 120%. The thicknessof the carbon-based protective layer 340 may be between about 5 Å andabout 200 Å. In one embodiment, the carbon-based protective layer is anamorphous carbon (a-C) layer. The amorphous carbon may be undoped ordoped with nitrogen. In one example, the carbon-based protective layer340 is a nitrogen-doped amorphous carbon layer. The nitrogen-dopedamorphous carbon layer may be deposited by any suitable depositiontechniques such as plasma enhanced chemical vapor deposition (PECVD)process. In one embodiment, the nitrogen-doped amorphous carbon layermay be deposited by flowing, among others, a hydrocarbon source, anitrogen-containing gas such as N₂ or NH₃, a plasma-initiating gas, anda dilution gas into a PECVD chamber. In another embodiment, thenitrogen-doped amorphous carbon layer may be deposited by flowing, amongothers, a hydrocarbon source, a nitrogen-containing hydrocarbon source,a plasma-initiating gas, and a dilution gas into a PECVD chamber. In yetanother embodiment, a nitrogen-containing hydrocarbon source, aplasma-initiating gas, and a dilution gas are flowed into the PECVDchamber to form the nitrogen-doped amorphous carbon protective layer onthe patterned features 321 and the exposed surfaces of the substrate300.

The hydrocarbon source may be a mixture of one or more hydrocarboncompounds. The hydrocarbon source may include a gas-phase hydrocarboncompound and/or a gas mixture including vapors of a liquid-phasehydrocarbon compound and a carrier gas, as will be further discussedbelow. The plasma-initiating gas may be helium since it is easilyionized; however, other gases, such as argon, may also be used. Thedilution gas may be an easily ionized, relatively massive, andchemically inert gas such as argon, krypton, xenon. In some cases,additional hydrogen dilution can be introduced to further increase thefilm density, as will be discussed later.

The hydrocarbon compounds may be partially or completely dopedderivatives of hydrocarbon compounds, including fluorine-, oxygen-,hydroxyl group-, and boron-containing derivatives of hydrocarboncompounds. The hydrocarbon compounds may contain nitrogen or bedeposited with a nitrogen-containing gas, such as ammonia, or thehydrocarbon compounds may have substituents such as fluorine and oxygen.Generally, hydrocarbon compounds or derivatives thereof that may beincluded in the hydrocarbon source may be described by the formulaC_(x)H_(y), where x has a range of between 1 and 20, and y has a rangeof between 1 and 20. In another embodiment, the hydrocarbon compounds orderivatives thereof that may be included in the hydrocarbon source maybe described by the formula C_(x)H_(y)F_(z), where x has a range ofbetween 1 and 24, y has a range of between 0 and 50, and z has a rangeof 0 to 50, and the ratio of x to y+c is 1:2 or greater. In yet anotherembodiment, the hydrocarbon source may be described by the formulaC_(a)H_(b)O_(c)F_(d)N_(e) for oxygen and/or nitrogen substitutedcompounds, where a has a range of between 1 and 24, b has a range ofbetween 0 and 50, c has a range of 0 to 10, d has a range of 0 to 50, ehas a range of 0 to 10, and the ratio of a to b+c+d+e is 1:2 or greater.

Suitable hydrocarbon compounds include one or more of the followingcompounds, for example, alkanes such as methane (CH₄), ethane (C₂H₆),propane (C₃H₈), butane (C₄H₁₀) and its isomer isobutane, pentane (C₅H₁₂)and its isomers isopentane and neopentane, hexane (C₆H₁₄) and itsisomers 2-methylpentance, 3-methylpentane, 2,3-dimethylbutane, and2,2-dimethyl butane, and so on. Additional suitable hydrocarbons mayinclude alkenes such as ethylene, propylene, butylene and its isomers,pentene and its isomers, and the like, dienes such as butadiene,isoprene, pentadiene, hexadiene and the like, and halogenated alkenesinclude monofluoroethylene, difluoroethylenes, trifluoroethylene,tetrafluoroethylene, monochloroethylene, dichloroethylenes,trichloroethylene, tetrachloroethylene, and the like. Also, alkynes suchas acetylene (C₂H₂), propyne (C₃H₄), butyne (C₄H₆), vinylacetylene andderivatives thereof can be used as carbon precursors. Additionallycyclic hydrocarbons, such as benzene, styrene, toluene, xylene,ethylbenzene, acetophenone, methyl benzoate, phenyl acetate,phenylacetylene (C₈H₆), phenol, cresol, furan, alpha-terpinene, cymene,1,1,3,3,-tetramethylbutylbenzene, t-butylether, t-butylethylene,methyl-methacrylate, and t-butylfurfurylether, compounds having theformula C₃H₂ and C₅H₄, halogenated aromatic compounds includingmonofluorobenzene, difluorobenzenes, tetrafluorobenzenes,hexafluorobenzene and the like can be used. Halogenated hydrocarbonssuch as carbon tetrachloride (CCl₄), diiodomethane (CH₂I₂),chlorofluorocarbon (CFC), bromotrichloromethane (BrCCl₃),1,1-dichloroethylene, bromobenzene, or derivatives thereof may also beused.

Examples of suitable derivatives of hydrocarbon compounds may include,but not limited to fluorinated alkanes, halogenated alkanes, andhalogenated aromatic compounds. Fluorinated alkanes may include, but notlimited to monofluoromethane, difluoromethane, trifluoromethane,tetrafluoromethane, monofluoroethane, tetrafluoroethanes,pentafluoroethane, hexafluoroethane, monofluoropropanes,trifluoropropanes, pentafluoropropanes, perfluoropropane,monofluorobutanes, trifluorobutanes, tetrafluorobutanes,octafluorobutanes, difluorobutanes, monofluoropentanes,pentafluoropentanes, tetrafluorohexanes, tetrafluoroheptanes,hexafluoroheptanes, difluorooctanes, pentafluorooctanes,difluorotetrafluorooctanes, monofluorononanes, hexafluorononanes,difluorodecanes, pentafluorodecanes, and the like. Halogenated alkenesmay include, but not limited to monofluoroethylene, difluoroethylenes,trifluoroethylene, tetrafluoroethylene, monochloroethylene,dichloroethylenes, trichloroethylene, tetrachloroethylene, and the like.Halogenated aromatic compounds may include, but not limited tomonofluorobenzene, difluorobenzenes, tetrafluorobenzenes,hexafluorobenzene and the like.

Nitrogen-containing hydrocarbon compounds or derivatives thereof thatmay be included in the nitrogen-containing hydrocarbon source can bedescribed by the formula CxHyNz, where x has a range of between 1 and12, y has a range of between 2 and 20, and z has a range of between 1and 10. Suitable nitrogen containing hydrocarbon compounds may includeone or more of the following compounds methylamine, dimethylamine,trimethylamine (TMA), triethylamine, quinoline, imidazole, vinylimidazole, acetonitrile, acrylonitrile, aniline, pyrrole, pyridine,piperidine, and benzonitrile.

In certain embodiments, oxygen-containing hydrocarbons compounds such asbenzaldehyde, acetophenone, anisole, diethyl ether, acetone, methanol,ethanol, isopropanol, ethanolamine, cresol, morpholine, or divinyl ethermay also be used in the deposition of amorphous carbon film.

The plasma-initiating gas may be introduced into the PECVD chamber atbefore and/or same time as the hydrocarbon compound and a plasma isinitiated to begin deposition. The plasma-initiating gas may be a highionization potential gas including, and not limited to, helium gas,hydrogen gas, nitrogen gas, argon gas and combinations thereof. Theplasma-initiating gas may also be a chemically inert gas, such as heliumgas, nitrogen gas, or argon gas. Suitable ionization potentials forgases are from about 5 eV (electron potential) to 25 eV. Theplasma-initiating gas may be introduced into the PECVD chamber prior tothe nitrogen containing hydrocarbon source and/or the hydrocarbonsource, which allows a stable plasma to be formed and reduces thechances of arcing.

An inert gas is typically used as a dilution gas or a carrier gas toflow with the hydrocarbon source, the plasma-initiating gas, thenitrogen containing hydrocarbon source, or combinations thereof.Suitable dilution gases may include argon (Ar), helium (He), hydrogen(H₂), nitrogen (N₂), ammonia (NH₃), noble gas such as krypton, xenon, orany combinations thereof. In one example, argon is used as the dilutiongas for reasons of economy. Ar, He, and N₂ may be used to control thedensity and deposition rate of the amorphous carbon layer. In somecases, the addition of H₂ and/or NH₃ can be used to control the hydrogenratio of the amorphous carbon layer. In cases where alkynes such asacetylene (C₂H₂) or alkenes such as propylene is used as hydrocarbonsource, the carrier gas may not be used during the deposition.

Conformality of amorphous carbon can be optimized by choice ofprecursors and deposition conditions. In general, precursors with lowerH:C ratio (<1:1 ratio) yield higher conformality. Exemplary processconditions for deposition of a conformal amorphous carbon film aredescribed below.

A hydrocarbon source, a nitrogen-containing gas and a dilution gas maybe introduced into a PECVD chamber to deposit a nitrogen-doped amorphouscarbon. The hydrocarbon source may be any suitable hydrocarbon compoundas discussed above. If a liquid hydrocarbon source is used, theprecursor flow may be between about 50 mg/min to about 1000 mg/min. If agaseous hydrocarbon source is used, the precursor flow may be betweenabout 100 sccm to about 5000 sccm, for example about 200 sccm to about600 sccm. If a carrier gas is used, the carrier flow may be betweenabout 500 sccm and about 10000 sccm. The plasma-initiating gas may beany suitable plasma-initiating gas as discussed above, and flowed at aflow rate from about 0 sccm to about 50,000 sccm, for example, betweenabout 400 sccm to about 8,000 sccm. The dilution gas may be any dilutiongas as described above and supplied at a flow rate from about 0 sccm toabout 5,000 sccm, for example about 500 sccm to about 1,000 sccm.

In various embodiments, the nitrogen-containing gas may be introduced ata nitrogen-containing gas to hydrocarbon source ratio of about 1:100 toabout 20:1, for example about 1:40 to about 10:1. The dilution gas maybe introduced at a dilution gas to hydrocarbon source ratio of about 2:1to about 40:1, for example about 20:1 to about 30:1. In one embodiment,a volumetric flow rate of hydrocarbon source:nitrogen-containinggas:plasma-initiating gas:dilution gas is in a ratio of, for exampleabout 1:1:0.5:20, for example about 1:0.5:0.5:20, for example about1:0.2:0.5:20, for example about 1:0.2:0.5:30, for example about1:0.2:0.5:40. In one embodiment, a volumetric flow rate of hydrocarbonsource:plasma-initiating gas:dilution gas is in a ratio of about1:0.5:20 to about 1:10:20, for example about 1:0.8:20, about 1:1:20,about 1:1.5:20, about 1:1.8:20, about 1:2:20, about 1:2.5:20, about1:3:20, about 1:3.5:20, about 1:4:20, about 1:4.5:20, about 1:5:20,about 1:5.5:20, about 1:6:20, about 1:8:20, about 1:10:20 or above, forexample about 1:15:20.

If a nitrogen-containing hydrocarbon source (as described above) isused, the nitrogen-containing hydrocarbon gas may be flowed at a flowrate from about 10 sccm to about 2,000 sccm, for example, from about 500sccm to about 1,500 sccm. In case the nitrogen-containing hydrocarbonsource is a liquid precursor, the nitrogen-containing hydrocarbon sourceflow can be between 15 mg/min and 2,000 mg/min, for example between 100mg/min and 1,000 mg/min. In one embodiment, a volumetric flow rate ofnitrogen-containing hydrocarbon source: the plasma-initiatinggas:dilution gas is in a ratio of, for example about 1:0.5:20, forexample about 1:0.2:20, for example about 1:0.8:20, for example about1:1:20, for example about 1:0.5:30, for example about 1:0.5:40.

During the deposition, the substrate temperature may be maintainedbetween about 75° C. to about 650° C., for example between about 80° C.and about 550° C., such as between about 300° C. and about 480° C., inorder to minimize the coefficient of absorption of the resultant film.The process chamber may be maintained at a chamber pressure about 100mTorr to about 100 Torr, for example from about 2 Torr to about 15 Torr,for example about 8 Torr or greater, such as about 20 Torr. Plasma maybe generated by applying RF power at a power density to substratesurface area of from about 0.001 W/cm² to about 5 W/cm², such as fromabout 0.01 W/cm² to about 1 W/cm², for example about 0.04 W/cm² to about0.07 W/cm². The power application may be from about 1 Watt to about2,000 watts, such as from about 10 W to about 100 W, for a 300 mmsubstrate. RF power can be either single frequency or dual frequency. Adual frequency RF power application is believed to provide independentcontrol of flux and ion energy since the energy of the ions hitting thefilm surface influences the film density. The applied RF power and useof one or more frequencies may be varied based upon the substrate sizeand the equipment used. If a single frequency power is used, thefrequency power may be between about 10 KHz and about 30 MHz, forexample about 13.56 MHz or greater, such as 27 MHz or 60 MHz. If adual-frequency RF power is used to generate the plasma, a mixed RF powermay be used. The mixed RF power may provide a high frequency power in arange from about 10 MHz to about 60 MHz, for example, about 13.56 MHz,27 MHz or 60 MHz, as well as a low frequency power in a range of fromabout 10 KHz to about 1 MHz, for example, about 350 KHz. Electrodespacing, i.e., the distance between a substrate and a showerhead, may befrom about 200 mils to about 1000 mils, for example, from about 280 milsto about 300 mils spacing.

The process range as discussed herein provides a deposition rate for anitrogen doped amorphous carbon layer in the range of about 10 Å/min toabout 30,000 Å/min. One skilled in the art, upon reading the disclosureherein, can calculate appropriate process parameters in order to producea nitrogen doped amorphous carbon film of different deposition rates.The as-deposited nitrogen-doped amorphous carbon layer has an adjustablecarbon:nitrogen ratio that ranges from about 0.1% nitrogen to about 10%nitrogen, such as about 2% to about 6%. An example of nitrogen dopedamorphous carbon materials deposited by the processes described hereinis provided as follows.

Referring back to FIG. 2, at box 210, after the carbon-based protectivelayer 340 has been deposited conformally on the patterned features 321using the novel process discussed at box 208, the carbon-basedprotective layer 340 is anisotropically etched (a vertical etch) toexpose the substrate 300 in areas 311 and expose an upper surface ofpatterned features 321, resulting in patterned features 321 protected bycarbon-based sidewall spacers 341 (formed from the carbon-basedprotective layer 340), as shown in FIG. 3D.

At box 212, the patterned features 321 are removed using a conventionalplasma etching process or other suitable wet stripping process, leavingnon-sacrificial carbon-based sidewall spacers 341 as shown in FIG. 3E.The plasma etching process may be performed by bringing the substrate300 in contact with a plasma generated from a fluorine-based etchingchemistry to remove the patterned features 321. Due to the improvedmaterial quality and coverage, the carbon-based sidewall spacers 341 arenot damaged because they have very good selectivity to thefluorine-based reactive etching chemistry or the wet strip-basedchemistry. Upon removal of the patterned features 321, the remainingcarbon-based sidewall spacers 341 may be used as a hardmask for etchingthe underlying layer, layer stack, or structure. The process 200 hasbeen proved to be able to form non-sacrificial carbon-based sidewallspacers 341 with a gap space of about 2.47 nm and a core space of about2.93 nm.

Other variations of the process are contemplated. For example, insteadof using only one spacer material as discussed above in process 200, twodifferent kinds of spacer materials may be used. In such a case, the twospacer materials need to be selective to each other so that one can beremoved without affecting the other spacer material. Conformal amorphouscarbon deposited in accordance with the inventive process describedabove can be an ideal candidate for the spacer material for variouspattering processes using two spacer materials, such as a self-alignedtriple patterning (SATP) process, because amorphous carbon film offershigh selectivity to conventional silicon-based materials from both dryand wet strip stand points. Some possible process flows for SATP are asfollows: (1) carbon core patterning→1^(st) oxide spacerdeposition→1^(st) oxide spacer etch back→conformal carbon spacerdeposition→conformal carbon spacer etch back→removal of 1^(st) oxidespacer; or (2) oxide core patterning→conformal carbon 1^(st) spacerdeposition→conformal carbon 1^(st) spacer etch back→oxide spacerdeposition→oxide spacer etch back→removal of 1^(st) carbon spacer.Details of process (1) are discussed below in process 400 and relatedFIGS. 5A-5H.

FIG. 4 is a flowchart depicting steps associated with an exemplarypatterning process using two different spacer materials according toanother embodiment of the disclosure. FIGS. 5A-5H illustratecross-sectional views of a structure formed by the steps set forth inFIG. 4. Similarly, the concept of this embodiment is equally applicableto other patterning processes such as a self-aligned double patterning(SADP) process, a self-aligned triple patterning (SATP) process, aself-aligned quadruple patterning (SAQP) process, a via/hole shrinkprocess, a back end of line (BEOL), etc., that may require the use ofprotective spacer or protective sacrificial layer, as needed in varioussemiconductor processes such as NAND flash application, DRAMapplication, or CMOS application, etc.

The process 400 starts at box 402 by providing a substrate 500 into aprocessing chamber, such as a PECVD chamber. The substrate 500 may beone or more materials used in forming semiconductor devices including asilicon material, an oxide material, a polysilicon material, or thelike, as discussed above with respect to substrate 300 shown in FIG. 3A.

At box 404, a non-sacrificial structural layer 520 is deposited on thesubstrate 500 as shown in FIG. 5B. The non-sacrificial structural layer520 may be a carbon-based material such as amorphous carbon. In oneexample, the carbon-based material is amorphous hydrogenated carbon. Oneexemplary carbon-based material that can be used as the sacrificialstructural layer 520 is an Advanced Patterning Film™ (APF) material,which is commercially available from Applied Materials, Inc. of SantaClara, Calif.

At box 406, a bottom anti-reflective coating (BARC) layer 540 isdeposited over the non-sacrificial structure layer 520. The BARC layer540 may be an organic material such as polyamides and polysulfones. TheBARC layer 540 is believed to reduce reflection of light duringpatterning of the subsequent resist layer and is also helpful forthinner resist layers because the BARC layer 540 increases the totalthickness of the multi-layered mask for improved etch resistance duringetch of underlying layer or structure. In some embodiments, a lightabsorbing layer 530 may be optionally deposited between the BARC layer540 and the non-sacrificial structure layer 520, as shown in FIG. 5C, toimprove photolithography performance. The light absorbing layer 530 maybe a metal layer, such as nitrides. In one example, the light absorbinglayer 530 is titanium nitride.

At box 408, a resist layer, such as a photoresist material, is depositedon the BARC layer 540. The resist layer is then patterned by alithographic process to form a patterned resist layer 550 with a desiredetch pattern 551, as shown in FIG. 5D. The etch pattern 551 may havedifferent pattern width, depending upon the application.

At box 410, the BARC layer 540, the light absorbing layer 530, and thenon-sacrificial structure layer 520 are patterned sequentially usingconventional photolithography and etching processes to transfer thedesired etch pattern 551 into the non-sacrificial structure layer 520,leaving patterned non-sacrificial features 521, as shown in FIG. 5E.

At box 412, a first conformal layer is deposited conformally orsubstantially conformally on the patterned non-sacrificial features 521(formed from the non-sacrificial structural layer 520) and the exposedsurfaces of the substrate 500. The first conformal layer may comprise astrippable material having an etching rate different from the patternedsacrificial features 521. Suitable materials for the first conformallayer may include, for example, oxides such as silicon dioxide, siliconoxynitride, or nitrides such as silicon nitride. The first conformallayer is then anisotropically etched to expose the substrate 500 inareas 511 and expose an upper surface of patterned non-sacrificialfeatures 521, resulting in patterned non-sacrificial features 521protected by strippable sidewall spacers 561 formed from the firstconformal layer, as shown in FIG. 5F.

At box 414, non-sacrificial carbon-based sidewall spacers 571 are formedadjacent or in contact with the patterned non-sacrificial features 521.The non-sacrificial carbon-based sidewall spacers 571 may be formed bydepositing a conformal layer of a carbon-based material, such as anamorphous carbon, either doped or undoped, on the substrate, coveringexposed surfaces of patterned non-sacrificial features 521, strippablesidewall spacers 561 and the substrate. The conformal amorphous carbonis deposited at least on top of the strippable sidewall spacers 561 suchthat this acts as a protective layer during the subsequent spaceretch-back process. The thickness of the conformal amorphous carbon maybe chosen based on integration requirements, typically between 10 Å and200 Å. Having excellent conformality (>95%) is important to ensure thatthe side-wall of the strippable sidewall spacers 561 is coveredadequately even with a very thin layer of carbon film (i.e. <50 Å).

In one example, the conformal layer of amorphous carbon is doped withnitrogen using the hydrocarbon compounds and processes described abovewith respect to boxes 208 and 210. The amorphous carbon layer, whendeposited using novel process conditions as discussed above (boxes 208),will achieve step coverage of at least about 80% or more, for exampleabout 100% or more, such as 120%.

The deposited conformal layer of amorphous carbon is thenanisotropically etched to expose surfaces of the substrate 500 in areas511 and expose upper surfaces of patterned non-sacrificial features 521and strippable sidewall spacers 561, resulting in patternednon-sacrificial features 521 protected by strippable sidewall spacers561 formed from the first conformal layer and non-sacrificialcarbon-based sidewall spacers 571 adjacent or in contact with strippablesidewall spacers 561, as shown in FIG. 5G.

At box 416, the strippable sidewall spacers 561, located between thepatterned non-sacrificial features 521 and the non-sacrificialcarbon-based sidewall spacers 571, are removed using a conventional wetstripping process or other suitable etching process, leaving patternednon-sacrificial features 521 and non-sacrificial carbon-based sidewallspacers 571 as shown in FIG. 5H. The remaining patterned non-sacrificialfeatures 521 and non-sacrificial carbon-based sidewall spacers 571 maythen be used as a hardmask for etching the underlying layer, layerstack, or structure. Particularly, the density of the resulting hardmask(i.e., patterned non-sacrificial features 521 and non-sacrificialcarbon-based sidewall spacers 571) in accordance with this patterningprocess is triple that of the patterned non-sacrificial features 521,and the pitch of resulting hardmask (i.e., patterned non-sacrificialfeatures 521 and non-sacrificial carbon-based sidewall spacers 571) ishalf the pitch of the patterned non-sacrificial features 521.

Carbon-based protective layers or carbon-based sidewall spacersdeposited in accordance with the present disclosure have been observedto be able to provide excellent conformality higher than 95% withimproved film properties, as shown below in Table 2, as compared to theconventional ALD grown spacers using silicon oxide materials. Since thesidewalls of hard mask spacers are not damaged during the ashing oranisotropic plasma etching process, the line edge roughness issignificantly reduced. Therefore, the resulting hard mask spacers canprovide superior etch profile and etch selectivity with little or nomicroloading. Table 1 below shows film properties of an amorphous carbonfilm deposited using the process conditions described above with respectto box 208.

TABLE 1 Uniformity (R/2, %) ~1.5% Refractive Index (633 nm) 1.7-1.9Absorption Coefficient (633 nm) 0.01-0.3  Film Density (g/cc) 1.25-1.70Stress (MPa) −100 to +100 Hardness (GPa) 2.5 Modulus (GPa) 20 StepCoverage (%) >100 Micro-loading (%) <3 Etch Selectivity to Poly 2.2

Conformal amorphous carbon layers deposited in accordance with thepresent disclosure may be used in various applications, such as contactCD (critical dimension) shrink process flow (for mask open, via etchetc.) at high temperatures (>300° C.) or low temperatures (<200° C.) forsmall CD requirement in 65 nm or beyond technology (e.g., 45 nm or even32 nm node technology in the future), CD control of high aspect ratio in3D NAND structure of oxide-nitride and oxide-polySi stacks, gap fill athigh temperatures (>300° C.) for self-aligned double patterning (SADP).

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

The invention claimed is:
 1. A method of forming a conformal amorphouscarbon layer on a substrate in a processing chamber, comprising:depositing a dielectric layer on a substrate; depositing a sacrificialdielectric layer on an upper surface of the dielectric layer; forming apattern into the sacrificial dielectric layer by removing portions ofthe sacrificial dielectric layer to expose portions of the upper surfaceof the dielectric layer; introducing a hydrocarbon source, aplasma-initiating gas, and a dilution gas into the processing chamber,wherein a volumetric flow rate of hydrocarbon source:plasma-initiatinggas:dilution gas is in a ratio of 1:0.5:20; generating a plasma in theprocessing chamber to deposit a conformal amorphous carbon layer on theportions of the upper surface of the dielectric layer and on remainingportions of the sacrificial dielectric layer; selectively removing theamorphous carbon layer using an anisotropic etching process to exposeupper surfaces of the remaining portions of the sacrificial dielectriclayer and to expose the upper surface of the dielectric layer; andremoving the remaining portions of the sacrificial dielectric layer. 2.The method of claim 1, further comprising: introducing anitrogen-containing gas into the processing chamber.
 3. The method ofclaim 2, wherein the nitrogen-containing gas is introduced at anitrogen-containing gas to a hydrocarbon source ratio of about 1:40 toabout 10:1.
 4. The method of claim 1, wherein the plasma is generated inthe processing chamber at a deposition temperature of about 200° C. orless.
 5. The method of claim 1, wherein the hydrocarbon compoundcomprises acetylene (C₂H₂), ethylene (C₂H₄), ethane (C₂H₆), propylene(C₃H₆), propyne (C₃H₄), propane (C₃H₈), butane (C₄H₁₀), butylene (C₄H₈),butyne (C₄H₆), phenylacetylene (C₈H₆), or combinations thereof.
 6. Themethod of claim 1, wherein the hydrocarbon source is anitrogen-containing hydrocarbon source.
 7. The method of claim 6,wherein the nitrogen-containing hydrocarbon source is described by theformula CxHyNz, where x has a range of between 1 and 12, y has a rangeof between 2 and 20, and z has a range of between 1 and
 10. 8. Themethod of claim 7, wherein the nitrogen-containing hydrocarbon sourcecomprises one or more nitrogen containing hydrocarbon compounds selectedfrom the group consisting of methylamine, dimethylamine, trimethylamine(TMA), triethylamine, aniline, quinoline, pyridine, acrylonitrile,benzonitrile, and combinations thereof.
 9. The method of claim 1,wherein the amorphous carbon layer is a nitrogen-doped amorphous carbonhaving a carbon:nitrogen ratio of between about 0.1% nitrogen to about10% nitrogen.